1. Field of the Invention
The present invention belongs to the field of a separation control method of a node device in a tree-type delivery system formed by participation of plural node devices.
2. Discussion of the Related Art
A content delivery system employing a technology of ALM (Application Layer Multicast) bears a potential risk that delivery topology (content delivery path) is disturbed by separation of a node device (visual terminal). Particularly, in a case of a broadcast-type (tree-type) delivery system that emphasizes synchronism of content delivery, streams are not supplied to the node device connected as a lower hierarchy level in the delivery path of the separated node device unless a disconnection state of the delivery path that is caused by separation of the node device is recovered in a short time. Accordingly, there occur troubles such that reproduction of the content stops in the node device connected as the lower hierarchy level and chain disintegration of a downstream topology is promoted.
To cope with such the problems, there has been provided a conventional method of employing a redundant connection that plural upstream nodes being stream supply sources are provided, in other words, content delivery is received from plural node devices simultaneously to prepare the separation of node devices. In this case, it is possible to get a time extension until a new upstream node device is rediscovered because stream supply of the other upstream node devices is available, even a stream supply from a single upstream node device stops.
In a method that a plurality of upstream node devices are provided, there is disclosed an operation method that a state where a stream is not received from nodes other than a main node (a state that only a connection procedure is completed) is maintained, one of upstream node devices in a suspended state is selected upon the stream stop of the main node thereby resuming the stream supply promptly (Vide Patent Document 1).
Patent Document 1: Japanese Unexamined Patent Publication No. 2006-33514